A Fe76-xCoxSi2B21Cu dual-phase nanocrystalline powder with excellent electromagnetic absorption properties

Abstract

The application belongs to the field of electromagnetic absorption materials and provides a Fe 76‑x Co x Si2B 21 Cu biphase nanocrystalline powder, the chemical formula of the biphase nanocrystalline powder is Fe 76‑x Co x Si2B 21 Cu, wherein x=0-10. The application successfully prepares a novel biphase nanocrystalline alloy powder electromagnetic absorption material with a strongest reflection loss (RL) value of up to -59.51 dB and an optimal effective bandwidth of up to 7.68 GHz (10.08-17.76 GHz), and the special biphase nanocrystalline structure realizes excellent impedance matching and electromagnetic attenuation, and also provides guidance for research and development of electromagnetic absorption materials with more excellent performance.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic absorbing materials, and specifically relates to a Fe material with excellent electromagnetic absorption properties. 76- x Co x Si2B 21 Cu biphase nanocrystalline powder. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Electromagnetic absorbing materials can absorb the energy of electromagnetic waves projected onto their surface and convert this energy into heat or other forms of energy through various material losses. Ideal electromagnetic absorbing materials should be thin, lightweight, have a wide frequency band, and high strength. Over the past few decades, researchers have explored a variety of electromagnetic absorbing materials, among which magnetic metal powders are a very important class. Magnetic metal powders possess good soft magnetic properties and high permeability, primarily dissipating electromagnetic waves through mechanisms such as eddy current loss and natural resonance loss. However, traditional magnetic metal powders have high conductivity and a strong skin effect, meaning that incident electromagnetic waves can only exist on the surface of the electromagnetic absorbing material and cannot effectively penetrate its interior. This results in a short effective absorption bandwidth and low maximum reflection loss. Furthermore, the susceptibility to corrosion and poor environmental adaptability of traditional magnetic metal powders limit their widespread use in various fields.

[0004] Compared to traditional magnetic metal powders, biphase nanocrystalline alloy powders possess the unique structure of both nanocrystalline phases and amorphous matrices. The atoms in the amorphous phase do not exhibit long-range order and periodic regularity in three-dimensional space, but rather a state of short-range order and long-range disorder. Furthermore, they lack crystal defects such as dislocations and grain boundaries, resulting in excellent wear and corrosion resistance, allowing them to adapt to complex and variable external environments such as seawater. The soft magnetic nanocrystalline phase possesses high saturation magnetization and low coercivity, leading to high initial permeability and strong magnetic loss capability. Simultaneously, the non-metallic elements and amorphous phase in the biphase nanocrystalline alloy powder contribute to its high resistivity, suppressing eddy current loss, and its low dielectric constant optimizes impedance matching. Therefore, biphase nanocrystalline alloy powder materials are attracting increasing attention in the field of electromagnetic wave absorption as promising candidate materials. Zhang et al. prepared Fe using a mechanical ball milling method. 80.7 Si4B 13 Cu 2.3Nanocrystalline soft magnetic alloy powder was prepared and its electromagnetic wave absorption performance was studied. The results showed that the powder has excellent electromagnetic wave absorption performance in the X-band (8-12 GHz), with an optimal reflection loss of -50.5 dB and an optimal effective absorption bandwidth of 5.0 GHz. Chen et al. prepared FeCrMoNiPBCSi amorphous powder by gas atomization and achieved good impedance matching and strong electromagnetic wave attenuation by compositing it with organosilicon. The optimal reflection loss reached -60.3 dB at 7.08 GHz, but the optimal effective absorption bandwidth was only 2.30 GHz, which cannot meet the requirements of next-generation electromagnetic absorption materials. Moreover, the composition of the dual-phase nanocrystalline alloy powder suitable for electromagnetic wave absorption is still unclear.

[0005] Patent CN110993239A discloses a method for preparing an iron-cobalt based amorphous soft magnetic alloy. The method involves preparing amorphous strips using a strip spinning method, followed by annealing to obtain strip-shaped samples. However, the absorption performance of the strips still needs to be improved.

[0006] Patent CN109554635A discloses a method for preparing a porous amorphous soft magnetic composite material with strong microwave absorption performance. The method involves first placing the amorphous strip in a ball mill for ball milling, and then etching it to obtain porous amorphous powder. However, its microwave absorption strength still needs to be improved.

[0007] In summary, the preparation of thin, lightweight, wide-bandwidth, and strong electromagnetic absorbing materials often requires the control of the two-phase nanocrystalline structure through the combination of alloy composition and preparation process. However, the industry has yet to prepare an alloy material that combines excellent broadband and ultra-strong wave absorption performance. Summary of the Invention

[0008] To address the above problems, this invention provides a Fe with excellent electromagnetic absorption properties. 76-x Co x Si2B 21 Cu dual-phase nanocrystalline powder. This invention successfully prepared a novel dual-phase nanocrystalline alloy powder electromagnetic absorbing material with the strongest reflection loss (RL) value as high as -59.51dB and the best effective bandwidth as high as 7.68GHz (10.08-17.76GHz). Its special dual-phase nanocrystalline structure achieves excellent impedance matching and electromagnetic attenuation, and also provides guidance for the development of electromagnetic absorbing materials with better performance.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a Fe with excellent electromagnetic absorption properties. 76-x Co x Si2B 21 Cu dual-phase nanocrystalline powder, wherein the chemical formula of the dual-phase nanocrystalline powder is Fe.76-x Co x Si2B 21 Cu, where x = 0-10.

[0011] In some implementations, x = 0, 2, 4, 6, 8, or 10.

[0012] A second aspect of the present invention provides a Fe with excellent electromagnetic absorption properties. 76-x Co x Si2B 21 The preparation method of Cu dual-phase nanocrystalline powder includes:

[0013] Fe, Co, Si, Cu, and FeB were mixed and smelted under an inert atmosphere to obtain Fe. 76-x Co x Si2B 21 Cu alloy ingots;

[0014] Fe was prepared using a single copper roller melt spinning process. 76-x Co x Si2B 21 Cu amorphous stripes;

[0015] The Fe 76-x Co x Si2B 21 Cu amorphous ribbons were cut to less than 1 mm, ball-milled, and annealed to obtain Fe. 76-x Co x Si2B 21 Cu biphase nanocrystalline powder;

[0016] Where x = 0 - 10.

[0017] In some embodiments, the mass fraction of Fe is 99.99% or higher;

[0018] In some embodiments, the mass fraction of Co is 99.98% or higher;

[0019] In some embodiments, the mass fraction of Si is 99.9999% or higher;

[0020] In some embodiments, the mass fraction of Cu is 99.99% or higher;

[0021] In some embodiments, the mass ratio of Fe to B in the FeB is 5:1.

[0022] In some embodiments, the Fe 76-x Co x Si2B 21The thickness of the Cu amorphous strip is 20-25 μm and the width is 1.5-2 mm.

[0023] In some embodiments, the ball milling is performed using vacuum ball milling.

[0024] In some embodiments, the conditions for vacuum ball milling are: ball-to-material weight ratio of 30-32:1, rotation speed of 500-600 rpm, and a pause of 5-8 minutes every 0.5-0.6 hours during the ball milling process, with alternating forward and reverse rotation.

[0025] In some embodiments, the annealing process is carried out under an inert atmosphere, at a temperature of 673-678K, and for a time of 1-1.5h.

[0026] A second aspect of the invention provides annealing and Co content in regulating Fe 76-x Co x Si2B 21 Application of Cu dual-phase nanocrystalline powder in microwave absorption properties.

[0027] A third aspect of the present invention provides the above-described Fe 76-x Co x Si2B 21 Application of Cu biphase nanocrystalline powder in the preparation of electromagnetic absorbing materials.

[0028] Beneficial effects of the present invention

[0029] (1) This invention prepares a thin, lightweight, wide-bandwidth, and strong electromagnetic absorbing material. Its unique dual-phase nanocrystalline structure achieves excellent impedance matching and electromagnetic attenuation. The dual-phase nanocrystalline powder of this invention achieves a maximum reflection loss (RL) of -59.51 dB at 12.32 GHz, an effective bandwidth of 7.68 GHz (10.08-17.76 GHz) at a thickness of 1.69 mm, achieving absorption in half of the X-band and the entire Ku-band, and an effective bandwidth of 5.12 GHz (8.00-13.12 GHz) at a thickness of 2.09 mm, covering the entire X-band. It exhibits excellent broadband and super-strong absorption performance even at a thin thickness.

[0030] (2) Compared with unannealed nanocrystalline powder, the annealed nanocrystalline powder in this invention continues to maintain excellent wave absorption performance, and the strongest reflection loss (RL) shifts to the low frequency region.

[0031] (3) The preparation method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0033] Figure 1 .Fe 76-x Co x Si2B 21 XRD patterns of Cu (x = 0, 2, 4, 6, 8, 10): (a) Alloy strips. (b) Powder ball-milled for 90 h. (c) Powder annealed at 673 K;

[0034] Figure 2 Fe after ball milling and annealing 76-x Co x Si2B 21 Grain size of Cu (x = 0, 2, 4, 6, 8, 10);

[0035] Figure 3 .Fe 76-x Co x Si2B 21 DSC spectra of Cu (x=0,2,4,6,8,10): (a) alloy strips, (b) powder milled for 90h, (c) powder annealed at 673K;

[0036] Figure 4 Fe in different states 76-x Co x Si2B 21 Crystallization enthalpy curves of Cu (x=0,2,4,6,8,10);

[0037] Figure 5 SEM and EDS images of M6;

[0038] Figure 6 (a) and (b) show the Fe values ​​before and after annealing, respectively. 76-x Co x Si2B 21 Particle size distribution of Cu (x = 0, 2, 4, 6, 8, 10) powder. (c) Fe before and after annealing. 76-x Co x Si2B 21 Average particle size diagram of Cu (x=0,2,4,6,8,10) powder;

[0039] Figure 7 (a)M-Fe 76-x Co x Si2B 21 Cu and (b)A-Fe 76-x Co x Si2B 21Hysteresis loops of two Cu powders;

[0040] Figure 8 .M-Fe 76-x Co x Si2B 21 Cu and A-Fe 76-x Co x Si2B 21 Electromagnetic parameters of two types of Cu powder;

[0041] Figure 9 .M-Fe 76-x Co x Si2B 21 Cu and A-Fe 76-x Co x Si2B 21 The dielectric loss tangent (tanδ) of two Cu powders in the 2-18 GHz frequency range ε and the tangent of the magnetic loss angle tanδ μ ;

[0042] Figure 10 .M-Fe 76-x Co x Si2B 21 Cu and A-Fe 76-x Co x Si2B 21 C0 curves of two Cu powders in the frequency range of 2-18 GHz;

[0043] Figure 11 .M-Fe 76-x Co x Si2B 21 Cu and A-Fe 76-x Co x Si2B 21 Contour plots showing the variation of reflection loss of two types of Cu powder with thickness and frequency.

[0044] Figure 12 .Specific RL of each powder min f m , Δf RL<-10 and d m value.

[0045] Figure 13 The reflection loss of M6 powder at different thicknesses, the impedance matching variation with frequency at different thicknesses, and the attenuation coefficient α of M6 powder. Detailed Implementation

[0046] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0047] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0048] Example 1

[0049] In an electric arc melting furnace with argon as the protective atmosphere, Fe (99.99% by mass), Co (99.98%), Si (99.9999%), Cu (99.99%), and FeB (mass ratio 5:1) were fully melted to prepare a uniformly mixed Fe alloy with nominal composition. 76-x Co x Si2B 21 Cu (x = 0, 2, 4, 6, 8, 10) alloy ingots exhibited a mass loss of less than 0.5%. Amorphous ribbons with a thickness of approximately 25 μm and a width of approximately 2 mm were prepared using single-copper roller melt spinning technology. The amorphous ribbons were then cut to less than 1 mm using ceramic shears, and the different Fe fractions were processed using a planetary ball mill. 76-x Co x Si2B 21 Cu (x = 0, 2, 4, 6, 8, 10) strips were vacuum ball-milled to obtain biphase nanocrystalline alloy powder M-Fe. 76-x Co x Si2B 21 Cu, designated as (M0, M2, M4, M6, M8, M10), with a ball-to-material weight ratio of 30:1 and a rotation speed of 500 rpm. To prevent overheating of the mill jar, a 5-minute pause was performed every half hour of milling, alternating between forward and reverse rotation. Then, a portion of M-Fe was processed. 76-x Co x Si2B 21 Ball-milled Cu (x = 0, 2, 4, 6, 8, 10) powder was annealed at 673 K for 1 h under argon atmosphere to obtain A-Fe. 76-x Co x Si2B 21 Cu (x = 0, 2, 4, 6, 8, 10) powder, denoted as (A0, A2, A4, A6, A8, A10).

[0050] Example 2

[0051] The strips and powders prepared in Example 1 were tested, including:

[0052] The phase composition and microstructure of the strips and powder were characterized using Cu-Ka radiation X-ray diffraction (DMAX-2500PC) and transmission electron microscopy (JEOL JEM F200). The thermal properties of the alloy were investigated using differential scanning calorimetry (DSC) at a heating rate of 20 K / min. The morphology of the powder was characterized using scanning electron microscopy (G500). The particle size of the powder was then measured using a laser particle size analyzer (Mastersizer 2000). The saturation magnetization (Ms) and coercivity (Hc) of the material at room temperature with a maximum applied magnetic field of 1.5 T were investigated using a vibrating sample magnetometer (Lakeshore-7404). The ground and annealed powder was mixed with paraffin wax at a weight ratio of 7:3 and pressed under a hydraulic press at a pressure of 1000 Pa for 5 s. A coaxial ring with an inner diameter of 3.04 mm and an outer diameter of 7.00 mm was prepared using this mold. The composite dielectric constant and permeability were measured using a vector network analyzer (E5071C) in the frequency range of 2-18 GHz using the coaxial transmission method.

[0053] Example 3

[0054] X-ray diffraction was used to analyze Fe in different states. 76-x Co x Si2B 21 Structural analysis was performed on Cu (x = 0, 2, 4, 6, 8, 10) materials. Figure 1 (a) shows Fe 76-x Co x Si2B 21 XRD patterns of Cu (x = 0, 2, 4, 6, 8, 10) alloy strips show the relationship between the microstructure evolution of the alloys and the Co content. All alloy strips with different Co contents exhibit typical broad diffraction peaks, indicating an amorphous structure. However, strips with lower Co content show weak crystalline peaks at the broad diffraction peaks. These results suggest that appropriate Co addition is beneficial for improving Fe... 76-x Co x Si2B 21 Cu's amorphous forming ability. After 90 hours of mechanical ball milling, all powders precipitated α-FeCo and Fe₂B phases, such as... Figure 1 As shown in (b), the main diffraction peak is relatively broad, indicating partial crystallization of the ball-milled powder. After annealing, the intensity of the diffraction peaks increases, as shown in (b). Figure 1 As shown in (c), this is due to the significant increase in the average grain size of the alloy powder and the increase in crystallinity. It is worth noting that the FCC phase precipitated after annealing. The average grain size of α-FeCo precipitates with different Co contents before and after annealing was estimated by the Scherrer equation (1) based on the full width at half maximum (FWHM) at the diffraction peak (110) in the X-ray diffraction pattern. Figure 2As shown, the average grain size before annealing varies slightly with different Co contents. After annealing, the average grain size increases significantly, but all are nanoscale powders. This indicates that the precipitation of nanocrystalline phases of different sizes in the material can be controlled by ball milling amorphous strips and annealing.

[0055]

[0056] K is the Scherrer constant, D is the average thickness of the grain perpendicular to the crystal plane, B is the measured half-width at half-maximum of the diffraction peak of the sample, θ is the diffraction angle, and γ is the X-ray wavelength, which is 0.154056 nm.

[0057] Fe in different states was analyzed by DSC. 76-x Co x Si2B 21 The thermal properties of Cu (x = 0, 2, 4, 6, 8, 10) materials were studied. Figure 3 (a) shows the strip DSC curves. The results indicate that as the Co content increases, the crystallization process of the alloy changes from one peak to two peaks, with the first and second crystallization temperatures Tc and Td respectively. x1 and T x2 These represent the precipitation of α-Fe(Co,Si) and Fe(Co) boride phases from an amorphous matrix, respectively. When the Co content is low, T... x1 The disappearance of [a-Fe(Co,Si)] indicates the precipitation of α-Fe(Co,Si), which is consistent with the appearance of XRD diffraction peaks. Specifically, as the Co content increases from x=0 to x=8, T […]. x1 First decrease, then remain relatively stable, T x2 The value gradually increases from 773K to 797K, △T(T) x1 -T x2 The increase in Co content means that the increased Co content improves the thermodynamic stability of the amorphous component. Figure 4 Fe in different states 76-x Co x Si2B 21 The exothermic enthalpy curves of Cu (x=0,2,4,6,8,10) materials show that with increasing Co content, the crystallization enthalpy area of ​​the strip material first increases and then decreases, corresponding to an initial increase and subsequent decrease in the amorphous proportion. This also indicates that a suitable Co content is beneficial to the formation of the amorphous phase. Compared to the strips, after 90 hours of mechanical ball milling, the exothermic enthalpy area on the DSC curves of each component showed a significant decrease, such as... Figure 3 (a), (b) and Figure 4 As shown, the alloy powder has a higher degree of crystallization after ball milling, and the alloy powder M-Fe 76-x Co x Si2B 21The exothermic enthalpy area of ​​Cu (x=0,2,4,6,8,10) increases with increasing Co content, and the trend of the exothermic enthalpy area is consistent with that of the strip material, indicating that the strip containing more nanocrystalline phases still has more nanocrystalline phases after ball milling. After argon annealing at 673K, A-Fe 76-x Co x Si2B 21 Further crystallization of Cu (x = 0, 2, 4, 6, 8, 10) powder resulted in virtually no exothermic crystallization peak observed on the DSC curve. Figure 3 As shown in (c), the microstructure of the powder was observed using high-resolution TEM. It was found that the powder still consists of an amorphous and nanocrystalline dual-phase composition.

[0058] Figure 5 These are SEM and EDS images of M6 powder. From... Figure 5 The powder particles exhibit two main morphologies: flat, plate-like shapes and uneven, clustered shapes. The particle size is below 100 micrometers, and the elemental distribution shows good uniformity. The flat, plate-like shape of the mechanically ball-milled biphase nanocrystalline powder, with its large aspect ratio, is beneficial for improving surface dipole polarization and reducing eddy current losses, thus reducing electromagnetic wave reflection at the material surface and improving the material's electromagnetic wave absorption performance. This is a result of the combined effects of crushing and cold welding during ball milling. The crushing effect during ball milling breaks brittle crystallized particles into smaller particles. These smaller particles easily aggregate and adhere to larger particles, producing many uneven, clustered particles. This special surface structure causes multiple reflections and scattering of incident electromagnetic waves, enhancing the material's ability to absorb electromagnetic waves. The particle size and average size distribution of the alloy powder before and after annealing are shown in the figure. Figure 6 As shown, the particle size curves exhibit a normal distribution. However, a comparison reveals that the irregular polymerization of powder particles after annealing leads to a significant increase in size.

[0059] M-Fe 76-x Co x Si2B 21 Cu and A-Fe 76-x Co x Si2B 21 The hysteresis loops of two types of Cu dual-phase nanocrystalline powders are as follows: Figure 7 As shown. From Figure 7 As can be seen, both powders exhibit excellent soft magnetic properties. The inset shows the curves of Ms and Hc as a function of Co content. Figure 7In (a), Ms shows a slight increase followed by a decrease and then an increase with increasing Co content, reaching a maximum of 175.14 emu / g in M4 powder. Since the Ms of an alloy is mainly determined by its composition and microstructure, while Hc is affected by grain size, defect concentration, and the preparation and heat treatment processes, for nanocrystalline alloys, the Ms of the soft magnetic nanocrystalline phase is greater than that of the amorphous phase. Therefore, the increase in α-FeCo nanocrystals with increasing Co content promotes exchange coupling between grains, leading to a rapid increase in Ms. The decrease in Ms for M4 and M6 is due to the increase in the amorphous phase. When the Co content is high, the coercivity increases due to the corresponding increase in magnetostriction during crystallization. Furthermore, according to the random anisotropy model, the coercivity varies with grain size as follows: Hc∝D 6 The combined effect of the two causes Hc to show a trend of first increasing, then decreasing and then increasing again, with M6 powder reaching a minimum value of 43oe. Figure 7 Figure (b) shows the different changes in the magnetic properties of the alloys after annealing. The increase in Ms of the dual-phase nanocrystalline alloy powders with the same Co content after annealing is due to the precipitation of more α-FeCo phase nested in the residual amorphous matrix and the increased crystallinity, with A6 powder reaching a maximum of 189 emu / g. However, the decrease in Ms for A0 and A2 is due to the precipitation of more FCC phase and non-soft magnetic Fe2B phase. After annealing, the heat treatment process leads to a reduction in defects and a release of internal stress, causing a decrease in Hc, with A8 powder reaching a minimum of 12.8 ee.

[0060] Example 4

[0061] To investigate the electromagnetic absorption properties of the prepared powder, M-Fe was measured using a vector network analyzer. 76- x Co x Si2B 21 Cu and A-Fe 76-x Co x Si2B 21 The complex permittivity (ε) of two types of Cu dual-phase nanocrystalline powders in the frequency range of 2–18 GHz r =ε′-jε″) and complex permeability (μ r =μ′-jμ″) as Figure 8 As shown, the real parts (ε′ and μ′) of the complex permittivity and complex permeability represent the ability to store electrical and magnetic energy, while the imaginary parts (ε″ and μ″) represent the ability to lose electrical and magnetic energy. Dielectric loss mainly includes polarization loss and conductivity loss. Figure 8 (a) represents M-Fe 76-x Co x Si2B 21The ε′ of Cu powder shows a slight decreasing trend in the 2-18 GHz range, exhibiting a trend of first increasing, then decreasing, and then increasing again with increasing Co content. Interfacial polarization is the main polarization mechanism; particles with large surface areas have a strong interfacial polarization effect. Therefore, the significant decrease in the size of the flake-like powder at M6 and M8 leads to a weakening of interfacial polarization and a decrease in ε′. Furthermore, electrical conductivity σ is also an important factor affecting ε′; therefore, M0 has the largest flake size but still a relatively small ε′ because the electrical conductivity of Co-free nanocrystalline powder is low. On the other hand, the fluctuation of ε″ in the 2-18 GHz range shows obvious polarization relaxation behavior. After annealing, A-Fe... 76-x Co x Si2B 21 The ε′ of Cu dual-phase nanocrystalline powders all increase because the increased particle size after annealing promotes enhanced surface polarization, with particularly significant increases in A4 and A8. Furthermore, the new phase of the FCC structure precipitated after annealing creates new phase interfaces, promoting interfacial polarization. Additionally, the reduced defects after annealing lead to increased dipole interactions, which in turn promotes displacement polarization, resulting in an increase in ε′. It can be noted that ε″ exhibits a significant negative value in the high-frequency region, possibly due to the formation of a conductive mesh by the powder particles, radiating electromagnetic waves.

[0062] Within the test frequency range, the skin effect intensifies with increasing frequency, and the real part of the permeability μ′ of all powders decreases with increasing frequency. At 2 GHz, μ′ exhibits a trend of first increasing, then decreasing, and then increasing again with increasing Co content, with M4 powder reaching a maximum value of 2.09. Based on the empirical formula for initial permeability, we can obtain:

[0063] μi is proportional to the square of Ms. As the Co content increases, Ms first rises, then falls, and then rises again. It can be inferred that μ′ also shows a trend of first rising, then falling, and then rising again as the Co content increases.

[0064]

[0065] Ms: Saturation magnetization; K1: Magnetocrystalline anisotropy; λs: Magnetostriction coefficient; ε: Internal strain; β: Impurity volume concentration; δ: Domain wall thickness; d: Impurity particle size.

[0066] The imaginary part of the permeability, μ″, follows an inverted parabola across the entire frequency range, due to the uneven distribution of particles. Simultaneously, μ″ exhibits three resonance peaks (4-6 GHz, 8-10 GHz, 14-16 GHz), which can be attributed to natural resonance, eddy currents, and exchange resonance. According to the eddy current loss formula:

[0067] μ r "=3πμ0(μ′) 2 d 2fσ (3)

[0068] Where f is the electromagnetic wave frequency, d is the thickness of the absorbing material, σ is the electrical conductivity, and μ0 is the permeability of free space.

[0069] μ″ is directly proportional to the square of μ′, so the change of μ″ with Co content is consistent with that of μ′.

[0070] After annealing, with M-Fe 76-x Co x Si2B 21 Compared to Cu nanocrystalline powder, the decrease in μ′ for A0 and A2 powders is due to the decrease in Ms and the precipitation of more Fe2B. The increase in Ms and the decrease in Hc increase μ′, and the reduction in internal stress and crystal defects caused by annealing also contributes to the increase in μ′; therefore, μ′ increases for all other powders. Notably, μ″ shows a significant increase after annealing, improving the material's magnetic loss capability.

[0071] To further investigate M-Fe 76-x Co x Si2B 21 Cu and A-Fe 76-x Co x Si2B 21 The electromagnetic loss mechanism of two Cu powders is addressed by introducing the dielectric loss tangent (tanδ) in this invention. ε =ε″ / ε′) and the tangent of the magnetic loss angle (tanδ) μ =μ″ / μ′), which represent the magnitude of the dielectric loss and magnetic loss capability of the material, respectively. Figure 9 The curves showing the variation of the loss tangent in the range of 2-18 GHz are presented. The results indicate that the magnetic loss tangent tanδ before and after annealing... μ Much larger than the dielectric loss tangent tanδ ε This indicates that magnetic loss plays a major role in the dissipation of electromagnetic wave energy across the entire frequency range. The magnetic loss of a material mainly originates from hysteresis loss, eddy current loss, domain wall resonance, natural resonance, and exchange resonance. Hysteresis loss can be neglected in weak magnetic fields. Domain wall resonance is typically observed in multi-domain material systems and generally occurs at lower frequencies (<2 GHz). Furthermore, the eddy current loss of a material can be expressed by the following formula:

[0072] C0 = μ″(μ′) -2 f -1 (4)

[0073] Where f is the frequency of the electromagnetic wave.

[0074] If the magnetic loss of a material is only related to eddy current loss, then C0 should remain constant with frequency. The variation of C0 with frequency is as follows: Figure 10As shown. In fact, M-Fe 76-x Co x Si2B 21 The C0 of Cu powder gradually decreases with increasing frequency up to 7 GHz, and then fluctuates with further increases in frequency. Therefore, M-Fe 76-x Co x Si2B 21 The magnetic loss of Cu powder to electromagnetic waves includes not only eddy current loss, but also natural resonance and exchange resonance, with exchange resonance occurring in the high-frequency region. Figure 8 The magnetic resonance peaks of μ″ at 4.5 GHz and 8.5 GHz are natural resonances, while the magnetic resonance peak at 14.5 GHz is an exchange resonance. (A-Fe) 76-x Co x Si2B 21 The CO content of Cu powder gradually decreases with increasing frequency, and then remains relatively stable in the high-frequency region, therefore A-Fe 76-x Co x Si2B 21 The magnetic loss characteristics of Cu powder include natural resonance and exchange resonance, and in the high-frequency region, it is mainly eddy current loss.

[0075] The ability of a material to absorb electromagnetic waves can be represented by its reflection loss (RL). Based on transmission line theory, and combined with measured electromagnetic parameters and the thickness of the absorbing layer, the reflection loss (RL) can be calculated using the following formula:

[0076]

[0077]

[0078] Z in Z0 is the dielectric impedance; Z0 is the free-space impedance; μ r It is the complex permeability; ε r is the complex permittivity; f is the incident wave frequency; d is the thickness of the absorbing layer; c is the speed of light in a vacuum; j is the imaginary unit.

[0079] Figure 11 and Figure 12 The calculated M-Fe values ​​are given respectively. 76-x Co x Si2B 21 Cu and A-Fe 76-x Co x Si2B 21 Contour plots showing the reflection loss (RL) values ​​of two Cu powders as a function of thickness and frequency, and specific RL values ​​for each powder. min f m , Δf RL<-10 and d mValue. Generally, the frequency range where RL < -10dB corresponds to 90% microwave absorption is widely accepted as the effective absorption bandwidth (Δf). RL<-10 ).from Figure 12 As can be seen, M6 powder exhibits the best absorption performance with increasing Co content, achieving the optimal reflection loss (RL) at 12.32 GHz and a diameter (d) of 1.8 mm. min When Δf reaches -59.51dB and d is 1.69mm, RL<-10 It achieves a maximum bandwidth of 7.68 GHz (10.08–17.76 GHz), basically covering the entire Ku band (12–18 GHz) and part of the X band (8–12 GHz), with an effective bandwidth Δf of 2.09 mm thickness. RL<-10 The frequency band is 5.12 GHz (8.00–13.12 GHz), covering the entire X-band. It's not difficult to see that for all M-Fe... 76-x Co x Si2B 21 Cu powder and M0 powder have minimal RL min It is -50.71dB, but still exceeds -50dB, RL min The corresponding f values ​​all exceed 10 GHz, and the d values ​​are all less than 2 mm, remaining at a low level. Around 1.66 mm, the optimal effective absorption bandwidth ΔfRL < -10 for all powders exceeds 7.5 GHz. Compared to unannealed powders, the frequency corresponding to the optimal reflection loss (RLmin) shifts to the lower frequency region after annealing. This is due to the increase in permeability μr and dielectric constant εr. Furthermore, powders with higher Co contents exhibit even better optimal reflection loss (RLmin) after annealing. In summary, by adjusting the Co content and annealing to control electromagnetic parameters, materials can achieve superior electromagnetic wave absorption performance.

[0080] The reflection loss of a material is related to its impedance matching characteristics and attenuation coefficient. The formula for calculating impedance matching is: Z = |Z| in / Z0|, the closer Z is to 1, the better the impedance matching of the material, allowing more electromagnetic waves to enter the absorbing material and reducing electromagnetic wave reflection to near zero, thus improving the material's absorption performance. The attenuation coefficient (α) reflects the material's ability to attenuate electromagnetic waves and can be used to evaluate the synergistic enhancement effect of dielectric loss and magnetic loss. The RL, Z, and α of M6 at different thicknesses are shown below. Figure 13 As shown, when dm is 1.8mm, the impedance matching is optimal and the attenuation coefficient is excellent at 12.32GHz, achieving superior electromagnetic wave absorption performance. At higher frequencies, although the attenuation coefficient is even better, the impedance of M6 is significantly mismatched under different thicknesses, leading to a decrease in electromagnetic wave absorption performance.

[0081] This invention successfully prepared micron-sized biphase nanocrystalline alloy materials with excellent electromagnetic wave absorption performance using a combination of single-roller spinning and vacuum mechanical ball milling. The M6 ​​powder achieved an optimal reflection loss (RLmin) of -59.50 dB at 12.32 GHz and a diameter (d) of 1.8 mm, and a maximum bandwidth of 7.68 GHz (10.08–17.76 GHz) with ΔfRL < -10 at a diameter (d) of 1.69 mm, essentially covering the entire Ku band (12–18 GHz) and part of the X band (8–12 GHz). The soft magnetic nanocrystalline phase possesses high saturation magnetization and low coercivity, resulting in high initial permeability and strong magnetic loss capability. Simultaneously, the non-metallic elements and amorphous phases in the biphase nanocrystalline alloy powder contribute to its high resistivity, suppressing eddy current loss, and its low dielectric constant optimizes impedance matching. Furthermore, by adjusting the Co content and annealing, the electromagnetic parameters can be controlled to achieve even better electromagnetic wave absorption performance.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Fe 76-x Co x Si2B 21 Cu dual-phase nanocrystalline powder, characterized in that, The biphasic nanocrystalline powder has the chemical formula Fe 76-x Co x Si2B 21 Cu, wherein x = 6, 8 or 10; Fe 76-x Co x Si2B 21 Method for the production of copper dual-phase nanocrystalline powder: Fe, Co, Si, Cu, FeB were mixed under the protection of inert atmosphere, smelted, to obtain Fe 76-x Co x Si2B 21 Cu alloy ingot Fe 76-x Co x Si2B 21 Cu amorphous ribbons; The Fe 76-x Co x Si2B 21 Cu amorphous ribbon was cut to 1 mm or less, ball milled, and annealed to obtain Fe 76-x Co x Si2B 21 Cu dual-phase nanocrystalline powder; Wherein, x=6, 8 or 10; The strongest reflection loss value of the dual-phase nanocrystalline powder is -59.51 dB at 12.32 GHz, and the effective bandwidth is 7.68 GHz at a thickness of 1.69 mm; The rotation speed of the ball mill is 500-600 rpm.

2. The Fe 76-x Co x Si2B 21 Cu dual-phase nanocrystalline powder characterized in that, The mass fraction of the Fe is 99.99% and above; Or, the mass fraction of the Co is 99.98% and above; Or, the mass fraction of the Si is 99.9999% and above; Or, the mass fraction of the Cu is 99.99% and above; Or, in the FeB, the mass ratio of Fe to B is 5:

1.

3. The Fe with excellent electromagnetic absorption properties as described in claim 1 76-x Co x Si2B 21 Cu dual-phase nanocrystalline powder, characterized in that... The Fe 76-x Co x Si2B 21 The thickness of the Cu amorphous ribbon is 20-25 μm, and the width is 1.5-2 mm.

4. The Fe 76-x Co x Si2B 21 Cu dual-phase nanocrystalline powder characterized in that, The Fe 76-x Co x Si2B 21 The thickness of the Cu amorphous ribbon was 25 μm and the width was 2 mm.

5. The Fe3Si2B0.5 alloy having excellent electromagnetic absorbing performance according to claim 1, wherein the alloy is composed of Fe, Si, B and C. 76-x Co x Si2B 21 Cu dual-phase nanocrystalline powder, characterized in that, The ball mill is a vacuum ball mill.

6. The Fe 76-x Co x Si2B 21 Cu dual-phase nanocrystalline powder characterized in that, The ball-to-material weight ratio of the vacuum ball mill is 30-32:1, and during the ball milling process, every 0.5-0.6 h of rotation is followed by a pause of 5-8 min, and the rotation is alternated.

7. The Fe with excellent electromagnetic absorption properties as described in claim 1 76-x Co x Si2B 21 Cu dual-phase nanocrystalline powder, characterized in that... The annealing treatment is carried out in an inert atmosphere, the annealing temperature is 673-678 K, and the annealing time is 1-1.5 h.

8. annealing and Co content in the regulation of Fe 76-x Co x Si2B 21 Cu dual-phase nanocrystalline powder in the application of wave absorption performance.

9. The Fe of claim 1 76-x Co x Si2B 21 Use of Cu dual-phase nanocrystalline powder in the preparation of electromagnetic absorbing materials.

Images